N,M=map(int,input().split())

F=[1,1]

for i in range(80):
    F.append(F[-1]+F[-2])

if F[N-1]==M:
    print(0)
    exit()

if F[N-1]<M:
    print(-1)
    exit()

MINUS=F[N-1]-M

ANS=0
for i in range(N-3,-1,-1):
    if MINUS>=F[i]:
        ANS+=1
        MINUS-=F[i]

print(ANS)